It is known that an heavy vehicle can have steering rear axles to allow an easier manoeuverability especially when the working in narrow spaces is required.
At present the steering rear axles are usually controlled by oleodynamic or oleopneumatic devices which can be connected to a speedometer providing the action of a mechanical stop when the speed exceeds a fixed value. The speedometer is usually connectable to an electronic system which provides to send the signals both to the possible oleo-pneumatic device and to the mechanical stop.
More particularly, to obtain the centering of the rear axles by means of a cinematic connection of the same to an oleodynamic cylinder, nowadays solutions are applied where such cylinder is hydraulically controlled while its own respective stem is positioned through the action of sensing transducers electrically connected to an electronic system. In this case the placing of the stem does not require the presence of any fixed reference mechanical abutments.
According to an other solution the stem of the oleodynamic cylinder is positioned in middle stroke only by means of mechanical devices using a double pneumatic or oleodynamic cylinder external to the said first cylinder and connected thereto by means of any suitable cinematic chain.
A further solution comprises the positioning of the stem always by means of mechanical devices but with a double oleodynamic cylinder incorporated in said first cylinder.
These latter solutions comprise fixed mechanical abutments as reference and, when the stem reaches the predefined centering position for the axles, the oleodynamic feeding circuit of the cylinder is switched to a by-pass position.